Heat insulation



Aug. 7, 1934.

C. G. MUNTERS HEAT INSULATION l Filed April 2, 1954 MMM 39 laf isfPatented Aug. 7, 1934 lmAT INSULATION Carl Georg Munters, Stockholm,Sweden Application April z, 1934,'seria1 No. '316,666

In Sweden March 3, 1931 7 Claims. (Cl. 154-45) This application is inpart la continuation of my copending application Serial No. 595,411

led February 26, 1932.

My invention relates to insulationand more particularly to insulation ofthe character employing a. relatively small amount of solid materialarranged to form intervening spaces containing gaseous material.-

It has heretofore been proposed to form insu- 10 lation of sheets ofsolid material with intervening air spaces, said sheets in sc meAinstances being of metal foil, as aluminum foil, to provide surfaceshaving lhigh heat-reecting characteristics. If the layers of air are onthe order of one centimeter in thickness in the direction of heattransfer, the air in said layers is substantially dead and so far asreducing heat transfer by convection maximum efciency has been sub-.stantially obtained. gases have a lower heat conductivity than air andit might be expected that' insulation of the character above referred tocould be improved by replacing the air by such a gas of lower heatconductivity. I

I have discovered, however, that such is not the case and the amount ofheat transfer through insulation charged with a gas of lower heatconductivity may` in fa t be higher'than that for the same .insulationwhen charged with air. I/ have further discovered, on the other hand,that advantage may be taken of the lower heat conductivity -of suchgases in insulating .structures of the type above referred to if the'gas layers arel made materially narrower than the critical spacing forpreventing convection currents in intervening vertical layers of air,and although this involves an increase in the number of sheets orpartitions, and thereby in the weight of solid material used, the totalad- 40 vantage derived from the use of the gas of lower heatconductivity results in insulation of materially higher elciency thanthe best heretofore obtained by use of stagnant layers of air ofwhateverthickness.

of layers into which the should be greater as the specific Weight of thegas employed increases, to the end that convection currents within saidgas layers may be reduced to a minimum. Therefore, in accordance with myinvention, I provide a hermetically sealed enclosure which is chargedwith a suitable gas of lower heat conductivity than air at acorresponding temperature and pressure and the gas space is subdividedgas lled space is subdivided;V by partitions of It` is known thatcertain' In accordance with my discovery the numberv sheet materialwhich provide narrow gas spaces in the direction of heat transfer andwhich afford a minimum of conductive contacts or paths for conductionbetween said sheets or partitions.

As compared with the spacing heretofore used when stagnant air has beenemployed, the thick- .ness of the `gas layers in the direction of heattransfer bears an inverse relation` to the specific weight of` the lgaWidth of gas space in the direction of heat flow,

the heavier the gas the sheets partitions or s, whereby for a giventotal greater the number of which are employed.

Whereas 'a spacing of one centimeter or more is suitable for sheetsbetween air layers, for an insulation of average heat drop,

the spacing ac- 76 cording to thepresent inventionwill be lessthanoneecentimeter, and preferably not exceeding about 5 mm.,

less than 5 mm.

Furthermore, to minimize or all of the partitions or` vided with brightsurfaces and may be materially heat transier, some sheets may be protoreduce radiation,

and the members of the insulation in the direc` tion of heat flow aremade heat conductivity.

of a material of low 80 'Ihe invention will be further described in thefollowing specification of illustrative embodiments, though it will beclear that the invention is not limited to the embodiments specificallydisclosed.

Of the accompanying drawing, which forms a part of this specification:

Fig. 1 is a sectional view, 1-1 of Fig. 2, through a embodying theinvention;

Fig. 2 is a sectional 2-2 0f Fig. 1;

and

Fig. 4 is a ture.

The structure shown in taken lon the line slab of insulation view takenon the line View of part of the strucand 2,. on enlarged scale;

` sectional view of a modified struc- Figs. 1, 2 and 3 comprises ahermetically sealed casing including side walls 34 and end or transversewalls'35. The 100 slab is to act as a heat insulation between the spacesoutsidek and adjacent walls 34. Consequently the line or direction ofheat ow' is perpendicular to the planes of walls 34. Walls or plates 34may be corrugated or otherwise formed 105 and are of such thickness asto give the insulating element sufficient strength and resistance toshocks. These walls may be made of aluminum, iron,- or other for thepurpose.

gastight substance suitable 'Ihe walls should be able to 110 vmethane(CClzFz)-;

withstandV pressure uctuations of about 100 millimeters mercury due tovariations in atmospheric pressure. The end walls 35 are made ofmaterial of low heat conductive capacity, such, for instance, as cellonlose and camphor or like plasticizers), celluloid, pollopas (anartificial mass obtained by condensation of urea or its derivatives andformaldehyde in the presence of bases) or the like, or a nickel-ironalloy, for example of Z5-35% nickel. Walls 35, as anged over the walls34 and, when using one or more of the non-metallic substances, arepasted thereto by a suitable kind of paste, which, for instance, mayconsist of a mixture lof cellon'and vinepas (polymeric vinylacetate)dissolved in acetone.

Within the casing or element are a plurality of thin partitions 30 ofsheet material spaced by frames 31 of felt, porous paper composition orlike material having low heat conductive ca# pacity, which frames aremade suiliciently rigid for handling during manufacture by means ofsimilarly formed frames 32 of suitable material such as cardboard pastedto the felt or the like. The cardboard frames are also preferably pastedto the sheets 30. Sheet members 30 may be aluminum foils or the like.The sheets 30 are disposed transversely to the direction of flow ofheat.

Within the frames`31 and between the sheet` members are spacinglmembersmade of superimposed pieces of felt and cardboard pieces 33 similar tothe material of parts 31 and 32.

At least every other partition 30 preferably has bright heat reflectingAsurfaces in order to counteract heat transmission through the ele-4-ment due to radiation.

The other partitions may consist of paper or the like having less heatreecting capacity, since` their principal purpose is to provide suchnarrow gas layers as to substantially prevent movement of gas in the`layers, and thus prevent heat transfer byl convection.

lThe interior of lthe casing, and consequently the spaces between thepartitions 30 of sheet material are lled with a gas having a lowercoeicient of heat conductivity than air at corresponding pressure andtemperature. Thev preferred gases are sulfur hexailuoride (SFs): methylchloride (CHsCl), dichlorodirluorosulfuryl fluoride (SOaFz): methylbromide (CHaBr): and ethyliodide (02H51). All these gases are halogencompounds. Other suitable gases for certain insulations vare compoundsof sulphur such as sulphur 'dioxide (SO2) and carbon disulphide (CS2). Amixture of two or more ofl said gases may be used. The gas or gasmixture which is made use of should have a boiling point lower than thelowest temperature prevailing where the heat insulator is to be used.The' gas chosen should be insoluble inthematerial of which theinsulation is made and should not react with said material.

I have discovered that these heavy gases require a closer spacing thanthe critical spacing for air; and in general the spacing should bee1eser `the heavier the gas. with the gases above mentioned,theidistance between the partitions or foils is preferably less than 5millimeters in order to prevent convection of the In order that the gasmay enter all of the spaces between the partitions, the felt framesshown in Figs. 2 and 3, arev may be provided with small holesVcommunicating with Athe narrow space 36 between the frames and thetransverse walls verse walls may be made of a single strip secured andmade tight by an overlapping corner piece 38. A filling hole 39 isprovided which may be closed by a coverv pasted thereon.

When the insulation is made as shown in Figs. 1, 2, and 3, it ispreferable, thoughnot essential, to use a gas pressure approximately thesame as but slightly below atmospheric pressure, since, in suclr case,the preponderance of pressure acting on' the outside ofthe casing tendsto maintain the separating members in place. Y

Fig. 4 shows a construction'permitting a higher pressure to prevailinside the insulation thanoutside. In this embodiment, the partitionsare spaced by means of ring elements 40 placed around pins 41 of amaterial of low heat con'- ductivity, such, for instance, as baklite, to

35. The transwhich the outside walls or plates are secured by means ofscrews 42. A The gas may be introduced by evacuating and vfilling theinsulation casing while 'wholly containedin a pressure vessel, so thatthe pressure inside and outside the insulationvcasing can be maintainedthe same.

In the foregoing, I have described-an insulating unit in which some ofthe partitions have bright surfaces, as when using. aluminum foil,backed or unbacked, or alternate foil and paper partitions.v Theinvention may be carried out without the use of reecting surfaces. Forex- In such case, the spacing should be still closer than hereinbeforeindicated in order to obtain equivalent effect in preventing heattransfer by radiation. Paper may be used without special ample, thepartitions may be entirely of paper. 110

frame members-by crumpling the paper so as to have a minimum contact. Ihave found an advantageous spacing of paper sheets tobe about 0.6millimeter.

may pass through the vpaper partitions.

What I claim is:

l: A heat insulating structure comprising exterior c'onning walls, agashermetically enclosed therein and having a lower heat conductivity thanair at a corresponding pressure and temperature, and partitions formedof sheet material between said walls arranged transversely to thedirection of heat transfer for counteracting heat transmission bylradiation and convec4 tion, said partitions forming intervening gaseouslayers materially narrower than the critical .spacing for preventingconvection currents in intervening vertical layers of air.

2. A heat insulating structure comprising ex terior confining walls, agas hermetically enclosed therein and. having a lower heat conductivitythan that of air at a corresponding pressure and temperature, said gascomprising a -gaseous compoundv of the group including sulphurhexauoride, methyl chloride, dichlorodiuoromethane, sulfuryl fluoride,methyl bromide and ethyliodide, and partitions formed of sheet materialbetween said walls arranged transversely to the direction of heattransfer for counteracting heat transmission by radiation and coneouslayers materially narrower than the critical spacing for preventingconvection currents in intervening vertical layers of air.

Non-conductive` spacing pins 3. A. heat insulating structure comprising150 spaced walls to be maintained at diiere'nt temvestion, saidpartitionsforming intervening gas- .145

perature, other walls forming with the first mentioned walls ahermetically sealed casing, a gas in said casing heavier than air, and aplurality of partitions ofsheet material per centimeter distance betweenthe first-mentioned walls for dividing the gas into layers.

4. A heat insulating structure comprising exterior confining walls, agas hermetically enclosed therein and having a lower heat conductivitythan air at a corresponding pressure and temperature, and partitionsformed of sheet material between said walls arranged transversely to thedirection of heat transfer for counteracting heat transmissionby`radiation and convection, said partitions forming intervening gaseouslayers having a thickness in the direction of heat transfer not greaterthan 5 millimeters.

5. A heat insulating structure comprising exterior conining walls, a gashermetically enclosed therein and having a lower heat conductivity thanthat of air at a corresponding pressure and temperature, said gascomprising a gaseous compound of the group including sul-4 phur dioxideand carbon bisulfide, and partitions formed of sheet material betweensaid walls arranged transversely to ,the direction of heat transfer forcounteracting heat transmission by radiation and convection, saidpartitions forming intervening gaseous layers materially narrower thanthe critical spacing for preventing convection currents in interveningvertical layers of air.

6. AL heat insulating structure comprising exteriorv confining walls, agas heremetically enclosed therein and having a lower heat conductivitythan air at a corresponding pressure and temperature, partitions formedof sheet material between said walls arranged transversely to thedirection of heat transfer for counteracting heat transmission byradiation and convection. and pressure resisting members of low heatconductivity passing through the partitions.

7. A heat insulating structure comprising exterior confining walls, agas hermetically enclosed therein and having a lower heat conductivitythan air at a corresponding pressure and temperature, and partitionsformed of sheet material between said walls arranged transversely to thedirection of heat transfer for counteracting heat transmission byradiation and convection, said partitions forming intervening gaseouslayers whose thickness in the direction of heat transfer is less thanone centimeter and'of a thickness sufficient to substantially preventconvection currents in intervening vertical layers of

